Band-gap reference voltage circuit with feedback to reduce common mode voltage

Abstract

A relates to a band-gap reference-voltage arrangement includes a MOS differential amplifier (OA2) having two inputs and one output. A first bipolar transistor (Q3) has its base/emitter path coupled between one input of the differential amplifier and a specific junction point and has an emitter-collector path arranged in a first current path for carrying a first current. A second bipolar transistor (Q4) has its base/emitter path connected in series with a resistor (R6) between the other input of the differential amplifier and said junction point and has its emitter-collector path arranged in a second current path for carrying a second current. First and second transistors (P1), P2) supply said first and second currents to the first and second current paths. A feedback path is provided for feeding back the signal from the output of the differential amplifier to the first junction point and comprises a third transistor (Q5) whose base-emitter path is connected between said junction point and the output of the differential amplifier.

I claim: 
     
       1. A band-gap reference-voltage arrangement comprising: an MOS differential amplifier having two inputs and one output,   a first bipolar transistor whose base-emitter path is connected between one input of the differential amplifier and a first junction point and whose emitter-collector path is connected in a first current path for carrying a first current,   a second bipolar transistor whose base-emitter path is connected in series with a resistor between the other input of the differential amplifier and said first junction point and whose emitter-collector path is connected in a second current path for carrying a second current,   a series arrangement of a second and a third resistor coupled between a supply voltage terminal and an output terminal for taking off a reference-voltage, a second junction point between the second and the third resistor being coupled to the base of the second transistor,   the output of the differential amplifier being coupled to said output terminal of the arrangement,   means for supplying said first and second currents to said first and second current paths, characterized in that the first resistor is coupled between the base of the second transistor and said first junction point, which by means of the base-emitter path of a third transistor is coupled to one end of the series arrangement of the second and third resistor.   
     
     
       2. A band-gap reference-voltage arrangement as claimed in claim 1, characterized in that the base of the third transistor is coupled to the output terminal. 
     
     
       3. A band-gap reference-voltage arrangement as claimed in claim 1, characterized in that the base of the third transistor is coupled to said supply voltage terminal. 
     
     
       4. A band-gap reference-voltage arrangement as claimed in claim 3, characterized in that the first and second transistors are replaced by a first and a second array of transistors, respectively, the number of transistors in each array being equal and the transistors in each array being interconnected such that each transistor has its emitter-collector path connected in a current path carrying its respective said first and said second current, and has its base connected to an emitter of a next transistor, the emitter of the last transistor in each array being connected to a respective input of the differential amplifier, and the base of the first transistor in said first and second arrays being connected to said first junction point and to the first resistor, respectively. 
     
     
       5. A band-gap reference-voltage arrangement as claimed in claim 4, characterized in that the number of transistors in each array is two. 
     
     
       6. A band-gap reference-voltage arrangement as claimed in claim 1, characterized in that the first and second transistors are replaced by a first and a second array of transistors, respectively, the number of transistors in each array being equal and the transistors in each array being interconnected such that each transistor has its emitter-collector path connected in a current path carrying its respective said first and said second current, and has its base connected to an emitter of a next transistor, the emitter of the last transistor in each array being connected to a respective input of the differential amplifier, and the base of the first transistor in said first and second arrays being connected to said first junction point and to the first resistor, respectively. 
     
     
       7. A band-gap reference-voltage arrangement as claimed in claim 6, characterized in that the base of the third transistor is coupled to the output terminal. 
     
     
       8. A band-gap reference-voltage arrangement as claimed in claim 1 wherein said means for supplying said first and second currents comprise a current mirror circuit having an input branch including a semiconductor diode and first and second output branches comprising first and second transistors, respectively, coupled to said first and second current paths, respectively. 
     
     
       9. A band-gap reference-voltage arrangement as claimed in claim 1 wherein said first resisftor is connected directly to the base of the second transistor and said first junction point is connected directly to the base of the first transistor. 
     
     
       10. A band-gap reference-voltage arrangement as claimed in claim 1 wherein said first resistor is connected directly between said first and second junction points.